Apparatus for forwarding tow

ABSTRACT

A fluid jet apparatus for receiving a ribbon of parallel continuous filaments, then heating and spreading the filaments for deposit on a moving surface as a nonwoven web includes an adjustable diffuser connected to the outlet end of the jet. The diffuser comprises a pair of spaced plates, adjustable with respect to each other, mounted to the outlet end of the jet. The plates are arranged to form aspiration slots at one end between the jet and the plates. The slots open into a central converging passage formed by the plates for confining and diverting gas out the open sides of the diffuser. The particular structural arrangement of the plates with respect to the jet permits development of static pressure in the diffuser which in turn causes a large percentage of jet fluid to exit from the open edges of the diffuser, generally parallel to the moving laydown surface, while less fluid accompanies the filaments to the laydown surface to reduce web disturbance.

United States Patent Piper et al.

APPARATUS FOR FORWARDING TOW Inventors: Woodrow W. Piper, MT. Juliet;

Arthur Michael Porter, Madison, both of Tenn.

Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

Filed: Apr. 19, 1972 Appl. No.: 245,350

U.S. Cl. 19/65 T, 226/97 51] Dld 11/02 [58] Field of Search 19/65 T, 66T; 34/10, 156; 226/7, 97; 425/464 6] References Cited UNITED STATESPATENTS 3,286,896 11/1966 Kinney 226/97 3,325,906 6/1967. Franke 34/10.

Primary Examiner-Dorsey Newton Attorney-Howard P. West, Jr.

[5 7] ABSTRACT A fluid jet apparatus for receiving a ribbon of parallelcontinuous filaments, then heating and spreading the filaments fordeposit on a moving surface as a nonwoven web includes an adjustablediffuser connected to the outlet end of the jet. The diffuser comprisesa pair of spaced plates, adjustable with respect to each other, mountedto the outlet end of the jet. The plates are arranged to form aspirationslots at one end between the jet and the plates. The slots open into acentral converging passage formed by the plates for confining anddiverting gas out the open sides of the diffuser. The particularstructural arrangement of the plates with respect to the jet permitsdevelopment of static pressure in the diffuser which inturn causes alarge percentage of jet fluid to exit from the open edges of thediffuser, generally parallel to the moving laydown surface, while lessfluid accompanies the filaments to the laydown surface to reduce webdisturbance.

5 Claims, 5 Drawing Figures PATENTED BET 23 I973 SHEET 10F 3 FIG-1PATENIED 0U 23 I973 CONTROLLER l APPARATUS FOR FORWARDING TOW BACKGROUNDOF THE INVENTION This invention concerns an apparatus for receiving aribbon of parallel continuous filaments, heating to promote shrinkageand spreading for deposit on a moving surface as a nonwoven web.

Kinney, U.S. Pat. No. 3,338,992, describes a process for preparing auniform nonwoven web by forwarding a multifilament strand and applyingan electrostatic charge to the filaments while under tension supplied bya fluid jet to promote separation of the filaments when tension isreleased. The separated filaments are deposited as a nonwoven web on amoving collecting surface and may later be subjected to a heatingoperation to promote bonding. A particularly useful nonwoven web may beprepared in this way using filaments which developspontaneous'elongation in the heating operation. Kitson and Reese inU.S. Pat. No. 2,952,879, describe a method for preparing such filaments,which comprises passing polyethylene terephthalate filaments having acrystallinity of less than about 35 percent through a zone at atemperature of at least 90 C. for a time sufficient to shrink thefilaments between percent and 70 percent and thereafter cooling beforethe crystallinity reaches the maximum level achievable in the zone. Inthe preparation of nonwoven webs, the heating zone may consist of afluid jet device where the filaments are subjected to rapid heating by ahot gas usch as air or steam where the filaments undergo the.

required 20 to 70 percent shrinkage. The. jet device is preferably theslot type, i.e., a device wherein the filament passage is rectangular incross section. The flow of gas through the jet provides a sufficienttension on the filaments to forward them but insufficient to preventshrinkage. This tension is at least partially released as the filamentspass out of the jet and the filaments then become more susceptible tohandling in a diffuser.

The filaments emerging from the jet require particular treatment toavoid sticking in the diffuser and must be spread out into wider ribbonsto promote uniformity in the webs which are collected. Franke, US. Pat.No. 3,325,906 and De Gusman, US. Pat. No. 3,334,161, describe diffusersof the prior art. Both of these disclosures relate'to use of a diffuserattached to a jet of rectangular cross section.The diffusers operate byproviding four diverging walls which allow the gas to expand and slowdown as it travels through the diffuser. Filaments may also be spread ina gas stream by use of converging diffuser plates. Apparatus for suchpurpose has been described in Isakoff, US. Pat. No. 3,593,074.

SUMMARY OF THE INVENTION two generally rectangular slots. The other endsof the plates extend below the outlet end of the jet to form aconverging diffuser passage in axial alignment with the jet filamentpassage. The slots are in communication with the diffuser passage andthe outside of the jet for introducing air by aspiration into theprimary fluid stream, and the diffuser passage terminates in an exitslot. In the preferred embodiment, the diffuser passage has open sidesand from the jet outlet to th diffuser exit, the passage is formed ofsuccessive curved, straight and converging lengths.

One of said plates is pivotally mounted to the outlet end of the jet forswinging movement toward and away from the other plate to change thesize of the exit slot. Means are also provided for moving the pivotallymounted plate according to the forwarding conditions or static pressureexisting in the diffuser passage. Preferably, the exit slot has a widthless than the combined widths of the two rectangular slots formed nearthe outlet of the jet. The particular structural arrangement of theplates with respect to the jet permits development of static pressure inthe diffuser which in turn causes a large percentage of jet air to exitfrom the open edges of the diffuser, parallel to the moving laydownsurface, while less air accompanies the filaments to the laydown surfaceto disturb web formation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of thefluid jet and diffuser combination of thei invention.

FIG. 2 is a schematic diagram showing relative placement of the diffuserplates with respect to the jet walls and the pressure control system foradjusting the diffuser exit slot.

FIG. 3 is a schematic of the controller of FIG. 2.

FIGS. 4 and 5 are elevation and end views of diffuser plates with anedge control seal.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring to FIGS. 1and 2, a ribbon of continuous filament fibers 10 is forwarded by meansof a fluid slot jet 12 through a diffuser 14 toward an imperviousflexible belt 16 moving in the direction of the arrow and covering asuction means (not shown) for collection as a nonwoven web. The fluidjet 12 has a filament inlet 11 and a filament outlet 13 both ofrectangular cross section and the diffuser 14 has a rectangular filamententrance 15 for receiving a ribbon of filaments from the jet. Althoughonly one jet apparatus position has been illustrated, multiple positionsmay be provided wth the jet diffuser combination of the invention, thesebeing diagonally placed across a collecting belt as described by Knee inUS. Pat. No. 3,402,227 (FIG. 9).

The diffuser is characterized by two diffuser plates 18 which at theirupper ends are located in close proximity to the lower outside surfaces17 of each of the two wide walls of the jet at the outlet 13, sufficientspace being provided for aspiration of air through rectangularaspiration slots 20 between upper inside surface 19 of the diffuserplates and the outside surface 17 of the jet and the plates form adiffuser exit slot 22 which is rectangular in cross section. the insidesurfaces of the diffuser plates converge from the aspiration slots 20 tothe diffuser exit 22. At least one of the diffuser plates 18 isadjustable, pivoting on pins 24 to provide an exit slot 22 which at itsnarrowest setting has a width less than the combined widths of the twoaspiration slots 20. The two diffuser plates 18 form passage 26 toconfine the escaping gas from the jet and spread the gas stream, therebypromoting spreading of the filaments into a wider ribbon. Excess gas isdischarged through escape opening 28 on one or both sides of thediffuser 14. The upper inside surfaces 19 of the diffuser plates in theaspiration gaps 20 are inwardly curved to form with the lower outsidesurface 17 of the wide jet walls a generally converging-divergingchannel.

In the preferred apparatus, the diffuser passage 26 is characterized bya smooth curve starting at the upper inside surfaces 19 of the diffuserplates. Downstream, the surfaces become straight, as designated bylength 30, and continue toinflection point 32. The lower surfaces of thetwo diffuser plates converge in a length 34 and terminate in exit slot22. Because of the reduced area at the exit slot, air flow is reducedand a considerable portion of the air is diverted out the gas escapeopenings 28 between the two plates (FIG. 1).

Several variations of the diffuser contour are possible. One importantpoint, however, is that the contours of the two plates should converge.The two plates 18 preferably have areas of parallelism (defined bylengths 30 in FIG. 2). There must be no areas of divergence from jetoutlet slot 13 to diffuser exit slot 22.

The diffuser is fastened to the jet device by means of a bracket 42which is mounted to jet end plate by means of bolts 40. The mountinjbracket 42 is keyed for accurate placement underneath the jet by tab 44which assists in providing accurate placement with jet end plate 46. Onediffuser plate 18 is rigidly attached to mounting bracket 42 by means ofbolts 43. The other diffuser plate is mounted for swinging movementaround pivot 24. The width of diffuser exit slot 22 is adjusted by meansof air cylinder 25 and piston 23. An air supply provides pressureagainst piston 23 which in turn pushes against the pivotally mounteddiffuser plate 18 which it engages. An opposing pressure is exerted byair coming through the jet 12. The width of diffuser exit slot 22 iswidened by reducing pressure in the air supply and narrowed byincreasing pressure in th air supply.

When the diffuser plates are quite thin, pivot pins 24 may pass througha bracket 49 attached to the outside of the plate.

FIGS. 2 and 3 illustrate a combination swath width control system whichis adapted for release of fiber plugs which may develop in the exit ofthe diffuser. In this system, a sensor 50 is placed in the fixeddiffuser plate 18. This sensor is connected by tubing 56 to a pressurecontrol device 52 such as the Corning Schmitt trigger Model 191456. TheSchmitt trigger is a fluidic control element which is very sensitive topressure differential and has a low switching hysteresis. It may bebiased to operate at a prescribed pressure level and will switch whenthe control is slightly higher or lower than this prescribed level. Airfrom a regulated supply flows to the pressure control device 52 andvalve 54 such a a Corning Fluid Amp Interface Valve Model 192621- LP (40psig) through pipes 51 and 53. Air for the three-way valve 54 passesfirst through valve air restrictor 55.

The controller 52 includes Schmitt trigger 70, connected between airsupply line 51 and valve 54 and a pressure biasing system connected tothe trigger 70, line 51 and the sensor 50. The pressure biasing systemincludes pipe loops 80 and 81 between line 51 and trigger 70 with loop80 connected to a variable restrictor 83 and loop 81 connected to tubing56 leading to sensor 50. Guage 82 is connected parallel to loops 80 and81. In operation, the trigger 70 is biased by balancing loops 80, 81 sothat air flows straight through trigger 70 from inlet 71 to outlet 72and on through pipe 57 to valve 54. This pressure applied to valve 54holds the valve open admitting air to cylinder 25. Pressure in loops 80and 81 is adjusted via restrictor 83 to maintain a higher pressure inloop 80 than in loop 81 to keep the main air stream flowing through thetrigger as described. In addition, the pressure in loop is somewhathigher than the pressure in the diffuser passage so that there is a flowof air through sensor 50 into the diffuser. In the event a plug developsin the exit 22 of the diffuser, pressure will build up in the diffuserto an extent to cause pressure to build in loop 81 and switch the airstream flowing through the trigger 70 from the outlet 72 to outlet 73.This in turn diverts the air from valve 54 which closes cutting off airto cylinder 25. With air pressure cut off from the cylinder, thepressure build up in the diffuser 14 causes pivotally mounted plate 18to swing outwardly releasing the plug. Once the plug is released, thepressure drops to normal allowing the trigger 70 to reset.

The sensor 50, which is 3/32 inch diameter hole in the upper section ofthe fixed diffuser plate, is supplied, by the feedback circuit, with 0.5psig air so that bleed occurs into the diffuser. When a plug forms achange of internal pressure equivalent to as little as l inch of wateris enough to trigger release. An over-pressure of 3 inches of water is areasonable working level so as to allow for string up and swathadjustment by an operator without accidentally causing release.

Additional features are needed for diffusers which are located at eitheredge of the collecting belt 16. FIGS. 4 and 5 show a suitable design forthese edge diffusers. Essentially, one edge of the diffuser plate 60 iscut at to the top edge and a flexible edge control seal is added toprevent air from carrying filaments off the edge of the belt. This isseen in detail in FIG. 5 where the edge is partially closed by aflexible sheet 62 held by clamps 64. The flexible material and theclamps are fastened to the two diffuser plates 60 by bolts 66.

In operation of the invention, a ribbon 10 of electrostatically chargedfilaments of polyethylene terephthalate and polyethylene terephthalatecopolymers is drawn into the jet 12 by aspiration and is carried throughthe jet by means of hot air introduced through air duct 8 of FIG. 1. Theconstruction of the jet is similar to that of Cope, US. Pat. No.3,302,237. Under the influence of the hot air stream, th filamentsshrink while passing through jet apparatus. The temperature of the airin the jet is between 225 and 235 C. Upon issuing from the jet, thefilaments pass from filament outlet 13 of the jet into the filamententrance 15 of the diffuser. Air is aspirated through aspiration slots20.

Typically, a ribbon 10 is about 6 inches wide. The exit of the diffuserjis ibout 19 inches above belt 16 and is about 12 /2 to 13 inches inlengthTl: FIG. 1). The degree of spreading at the diffuser exit dependspartially upon the charge level. With a charge of about 2microcoulombs/gram the swath width may be varied for example from about23 inches to about 32 inches by changing the diffuser exit gap from0.280 inch to 0.150 inch. With a charge of about 4 microcoulombslgramthe swath width may be varied from about 31 to about 50 inches using thesame exit gap range. Each aspiration gap 20 is typically set with an0.250 inch width at the narrowest point.

What is claimed is:

1. In a filament forwarding apparatus including a jet having inlet andoutlet ends connected by a filament passage of generally rectangularcross section, a diffuser comprising: a pair of spaced plates mounted tothe outlet end of the jet, one end of-the plates extending above saidoutlet end and being spaced therefrom to form two generally rectangularslots, the other end extended below said outlet said plates forming anopen sided diffuser passage in axial alignment with said jet filamentpassage, said slots being in communication ith said diffuser passage andthe outside of the jet, said diffuser passage having successive curved,straight and converging lengths, said curved length being adjacent theoutlet endof the jet, said converging length terminating at said exitslot, the filaments being forwarded through the jet and diffuserpassages by a gas, said gas developing static pressure in the diffuser;and means for pivotally mounting one of said plates to the outlet end ofthe jet for swinging movement toward and away from the other plate tochange the size of the said exit slot.

2. The apparatus as defined in claim 1, said exit slot having a widthless than the combined widths of said two rectangular slots.

3. The apparatus as defined in claim 1, including means for moving saidpivotally mounted plate according to the static pressure in the diffuserpassage.

4. The apparatus as defined in claim 3, said means for moving accordingto the forwarding conditions in the diffuser passage comprising: apressure sensor in communication with said passage; an air cylinderengaging said one plate adjacent said exit slot; a source of pressurizedair connected to. said cylinder; and means for cutting air off from saidcylinder, said means being actuated by said sensor.

5. In a filament forwarding apparatus including a jet having inlet andoutlet ends connected by a filament passage of generally rectangularcross section, a diffuser comprising: a pair of spaced plates mounted tothe outlet end of the jet, said plates forming an open sided diffuserpassage in axial alignment with said jet filament passage, said diffuserpassage terminating in an exit slot; means for pivotally mounting one ofsaid plates to the outlet end of the jet for swinging movement towardand away from the other plate to change the size of the exit slot; apressure sensor in communication with said diffuser passage; an aircylinder connected to said one plate adjacent said exit slot; and acontrol means connected to said cylinder for admitting and releasing airto said cylinder for operating said cylinder to move said one plate,said control means being actuated by said sensor.

1. In a filament forwarding apparatus including a jet having inlet andoutlet ends connected by a filament passage of generally rectangularcross section, a diffuser comprising: a pair of spaced plates mounted tothe outlet end of the jet, one end of the plates extending above saidoutlet end and being spaced therefrom to form two generally rectangularslots, the other end extended below said outlet said plates forming anopen sIded diffuser passage in axial alignment with said jet filamentpassage, said slots being in communication with said diffuser passageand the outside of the jet, said diffuser passage having successivecurved, straight and converging lengths, said curved length beingadjacent the outlet end of the jet, said converging length terminatingat said exit slot, the filaments being forwarded through the jet anddiffuser passages by a gas, said gas developing static pressure in thediffuser; and means for pivotally mounting one of said plates to theoutlet end of the jet for swinging movement toward and away from theother plate to change the size of the said exit slot.
 2. The apparatusas defined in claim 1, said exit slot having a width less than thecombined widths of said two rectangular slots.
 3. The apparatus asdefined in claim 1, including means for moving said pivotally mountedplate according to the static pressure in the diffuser passage.
 4. Theapparatus as defined in claim 3, said means for moving according to theforwarding conditions in the diffuser passage comprising: a pressuresensor in communication with said passage; an air cylinder engaging saidone plate adjacent said exit slot; a source of pressurized air connectedto said cylinder; and means for cutting air off from said cylinder, saidmeans being actuated by said sensor.
 5. In a filament forwardingapparatus including a jet having inlet and outlet ends connected by afilament passage of generally rectangular cross section, a diffusercomprising: a pair of spaced plates mounted to the outlet end of thejet, said plates forming an open sided diffuser passage in axialalignment with said jet filament passage, said diffuser passageterminating in an exit slot; means for pivotally mounting one of saidplates to the outlet end of the jet for swinging movement toward andaway from the other plate to change the size of the exit slot; apressure sensor in communication with said diffuser passage; an aircylinder connected to said one plate adjacent said exit slot; and acontrol means connected to said cylinder for admitting and releasing airto said cylinder for operating said cylinder to move said one plate,said control means being actuated by said sensor.